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I Wonder Why – Why Cut Apple Turns Brown?

Brown color

Why does an apple turn brown on being cut?

● Apples,  and  other  fruits  like  pears,  bananas,  peaches,  potatoes,  contain  an 

The enzyme (called polyphenol oxidase or tyrosinase) reacts with oxygen, and 

iron-containing phenols that are also found in the apple. 

● The oxidation reaction forms a sort of rust on the surface of the fruit. 

You  see  the  browning  when  the  fruit  is  cut  or  bruised because  these  actions 

damage the cells in the fruit, allowing oxygen in the air to react with the enzyme 

and other chemicals. 

● These enzymes do all of the work necessary for the cell to live its life. Once you 

Cut the fruit,  you open up some of the cells. The enzyme then has access to 


oxygen in the air and it does its thing, turning the fruit brown. 

● This is the same thing that causes brown spots in apples when you drop them. It 

is  believed  that  this  reaction,  called  enzymatic  browning,  is  a  form  of  plant 

defense against pests and pathogens.

● The easiest way to prevent browning is to put the sliced apples in water so that 

the enzyme does not have access to oxygen. You can also heat the apples to 

denature the enzyme.